In order to solve the difficulty of load moment calculation of different cross section wires, a method of load moment normalization is proposed. In the case of ensuring the same voltage drop of the conductor, the model of wire can be unified through the normalization coefficient, and the complex distribution network is simplified and standardized. On this basis, the mapping relationship between the node load moment and the node voltage is established. Through the BP neural network based on the Levenberg-Marquardt algorithm, the full coverage estimation of the node voltage is realized, and the shortcomings of the traditional gradient descent algorithm in the convergence speed and the calculation stability are overcome. The required training samples are few, and the calculation efficiency is high. A practical network is selected for simulation analysis. The effectiveness of the proposed method is verified.